Design and Build

Design and Build procurement works on the basis that the main contractor is responsible for undertaking both the design and construction work on a project, for an agreed lump-sum price.

Design and build projects can vary depending on the extent of the contractor’s design responsibility and how much initial design is included in the employer’s requirements. Nevertheless, the level of design responsibility and input from the contractor is much greater on design and build projects than a traditional contract with a contractor’s designed portion.

Adequate time must be allowed to prepare the employer’s requirements (the employer usually appoints consultants to facilitate this), as well as time for the contractor to prepare their proposal and tender price. It is vital that the proposal matches all of the employer’s requirements before any contract is entered into.

The employer has control over any design elements of the project that are included in their requirements, but once the contract is let responsibility over design passes to the contractor, so the employer has no direct control over the contractor’s detailed design.

The contractor can carry out the design in a number of ways. Often they will appoint their own consultants or use their own in-house team. It is also common practice for the contractor to take on the employer's consultants and continue to use them to complete the detailed design under what is known as a novation agreement.

Other Features of Design and Build Procurement

  • As design and construction can be carried out in parallel, the overall programme time of design and build projects can be shorter. However this depends on how much design the contractor is responsible for.
  • There is reasonable certainty over costs because the contract price is known at the outset. Provided the employer does not order changes during the construction of the work, the contractor will be obliged (subject to the conditions) to complete the project for the contract sum. If the employer does require design or specification changes during the construction period, the contractor advises as to the effect this may have on costs or additional time needed.
  • Design and Build is a relatively low risk procurement option for the employer, in terms of cost and time. There can be a risk related to design and quality, particularly if the employer's requirements were not properly gathered and if insufficient time went into examining the contractor's proposal.

Types of Design and Build Contract

  • Package deal or turnkey contracts - This is where the employer accepts a proposal based on a standard design from the contractor, effectively providing a single point of responsibility as the contractor is responsible for the design and construction of the entire project.
  • Design and build contracts - This is where project documents are compiled with the contractor's design obligations relating to the whole of the works in mind. 

Design and Build JCT Contracts